I'm asking this here to avoid being conned by "professional" roofers in India who either exaggerate their estimates or send highly unskilled labourers to do the job.
D: Areas that are damaged
H: Drainage holes
P: Ponding areas (places where water accumulates and does not flow away)
C: Small cracks that may or may not be significant for consideration
D2 was an area where a solar water heater was installed and after it was removed, one strip of the roofing got damaged and cement was applied on it (as in the pic below). It hasn't caused any leak problems for 5 years, and the area only started leaking during last year's rains.
H1 and H2 are the only points for water drainage on the entire roof (I do believe the roof is slightly sloping toward H1 and H2). Because of D2 having some elevation, some of the water collecting in P1 was not able to flow to H2 (blue arrow) and was not flowing to H1 either.
1. Is it possible that the damages at D1 and D3 could cause water to seep into the damaged areas and eventually flow and accumulate at the D2 area, thus causing leakage inside the house?
2. A mason says that in order to waterproof D2, he'd first have to chip off some of the cement along that strip, then get some sand and cement and mix some waterproofing liquid (another mason said he'd mix a waterproofing powder) into the cement and then apply it over D2. He's offering to do it (and the repairs of D1 and D3) at less than half the price that professional roofers charge. Does his technique sound ok to you?
3. Is it ok if there is some ponding of water at P1 and P2 or should some cement be applied at least at P1, just to create a slope so that the water flows into H2 (won't that add extra weight to the roof)?
4. How does one determine whether cracks are just cracks on the plaster or whether they are deep enough to cause roof leaks? For example, the pictures below: